The present invention relates to an improvement in a cooling structure for internal combustion engines which is integral with a transmission case.
Power transmission units especially for use in automotive internal combustion engines are housed in transmission cases in hermetically sealed condition for waterproof and dustproof purposes. Such an arrangement has been disadvantageous in that the interior of the transmission case is subjected to a temperature rise due to heat generated by a variety of mechanical losses in the power transmission unit, such as heat caused by friction upon slippage between a belt pulley and a belt, and heat due to friction between sliding parts of bearings, and hence the components of a power transmission unit tend to be disadvantageously influenced by such generated heat.
With a crankcase to which a transmission case is integrally joined, the heating of the transmission case puts the latter out of thermal equilibrium. The crankcase as a whole suffers from thermal strain and thermal stress under such a thermally unbalanced condition, with the result that the crankcase will become poor in accuracy of assembly and mechanical strength. The present inventor has made the present invention in an effort to effectively and reasonably eliminate the foregoing difficulties experienced with a crankcase for an internal combustion engine, especially a crankcase integral with a transmission case.